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Biomedical subjects

P S Yip

Publications and source records attributed to P S Yip.

At least 19 recordsLinked to original sources

Parametric modelling of neonatal mortality in relation to size at birth.

We use a richly parameterized model to analyse the effects of shortness and thinness at birth on neonatal mortality in Swedish live-born singletons. The model captures the hazard of neonatal mortality according to the function alpha x exp(-gamma x t) + delta, where t represents age. Covariates are allowed to simultaneously influence the initial excess hazard, the rate of decay, and the long-term hazard. Among term newborns, birth length for gestational age had a stronger effect on the long-term hazard and a weaker effect on the initial excess hazard than the Ponderal index. The initial excess hazard associated with a low Ponderal index tended to decay quickly. Among preterm newborns, a higher birth length for gestational age was associated with lower initial and long-term hazards, and with a faster rate of decay of the initial excess hazard. In contrast, the Ponderal index was not associated with the long-term hazard. We discuss the interpretability of the model and its potential use in neonatology and medical demography. We also compare the model to a Cox model with time-dependent covariates.

Analysis of Variance↗

Psychosocial adjustment in gynecologic cancer survivors: a longitudinal study on risk factors for maladjustment.

OBJECTIVE: The objective was to describe the change in psychosocial state over time and to identify risk factors for maladjustment in gynecologic cancer survivors. Awareness of these issues is important for planning supportive care services for cancer patients. METHODS: A longitudinal prospective study of patients with newly diagnosed gynecologic cancer using individual patients as their own control was performed. Patients were interviewed after confirmation of the diagnosis and were reassessed at 6 and 18 months after completion of treatment and with no evidence of recurrent disease. Psychological adjustment was measured by self-rating on self-esteem, outlook on life, self-role, and femininity. Neuroticism and anxiety were assessed using a neuroticism score and the Hamilton Anxiety Scale. Depressive symptoms were questioned directly. Social adjustment was assessed by changes in working capacity or work status, leisure activity, marital relationship, and sexual activity. RESULTS: Seventy-four women participated. Adjustment problems did not occur in the majority of patients. Psychosocial adjustment was different for patients receiving different types of treatments. Improvement in feminism (P = 0.050) and neuroticism (P = 0.010) was observed for patients receiving chemotherapy and deterioration was observed in patients treated with surgery. Deterioration in neuroticism was associated with lower education level (P = 0.032). With religious belief, there was better family support and more significant improvement in social activity (P = 0.038). CONCLUSION: Most patients adapted well. Patients at risk for psychosocial maladjustment include those who are treated surgically, less educated, and without religious belief.

Adolescent↗

A longitudinal study on quality of life after gynecologic cancer treatment.

OBJECTIVE: The objective was to describe the pattern of quality of life (QOL) over time and to assess the impact of age, symptoms, disease parameters, and treatment on the overall QOL. METHODS: A longitudinal study on patients with newly diagnosed gynecologic cancer using individual patients as their own control was performed. The 33-item EORTC QLQ-C30(+3) was used as the QOL measure. Patients were assessed before treatment, after completion of treatment, and at 6, 12, and 24 months. Spearman's correlation analyses were performed. A mixed effect model was fitted to the data. Bonferroni pairwise comparisons were used to analyze the different variables. RESULTS: One hundred forty-four women completed the study. Overall QOL improved after the completion of treatment but remained the same throughout the 2 years after treatment. The individual patient's QOL before treatment was insignificant while the impact of treatment on the individual patient was significant in determining QOL after treatment. There was a strong correlation for all time points in most factors, indicating that the global health status, functional scales, and symptom scales exhibit a dependent change over time. Relief in symptoms was associated with improvements in functional scales. The scores on overall QOL were lower for younger patients and for patients treated with chemotherapy than for patients treated with surgery. CONCLUSIONS: Strategies for supportive care need to focus on symptom management. Psychosocial interventions, to be effective, should include all patients and should aim to reduce the impact of treatment on the individual patient.

Adult↗

The profile of bone mineral density in chinese women: its changes and significance in a longitudinal study.

Bone mineral density (BMD) has been shown to be different in different ethnic groups. When lifestyle and diet evolve, there is a possibility of a change in the normal reference BMD values within an ethnic group over a period of time. As the osteoporotic risk uses the T-score as the bench mark, it is pertinent to evaluate whether such changes do occur. Two measurements, 5 years apart, of the BMD of the spine and the hip were made in a cohort of Chinese women in Hong Kong. A kernel function smoothing method, a nonparametric statistical method, was employed to present the BMD data. The greatest rate of bone loss was found to occur between 50 and 59 years of age, but this rate of loss was reduced from age 60 onwards. The BMD values obtained in these two measurements were different from the previous studies in the same population and were found to be higher at the lumbar spine and neck of femur in women over 65 years of age. Even within the cohort, there seemed to be a reduction in the BMD values of the hip in a span of 5 years, although the differences were statistically insignificant. These studies suggest that BMD values could change in a population for a variety of possible reasons. Hence, the reference BMD values might need to be evaluated at regular intervals for the T-score to be meaningful.

Absorptiometry, Photon↗

Social patterns of birth weight in Hong Kong, 1984-1997.

Fetal growth is an indicator of social inequalities in health that may have a long-term impact persisting into later life. Little is known about the social patterns of birth weight in Hong Kong. This is a study of live-born singletons from 1984 to 1997 in a Hong Kong birth registry. Ordinary least-squares regression and logistic regression are used to analyse birth weight and low birth weight (< 2500 g), respectively. A gradient of birth weight and prevalence of low birth weight is demonstrated according to mothers' educational attainment. In relation to babies of the most educated mothers, babies of the least educated mothers had a mean deficit of 46g in birth weight and an odds ratio of 1.56 of low birth weight (each P<0.05). This social gradient was hidden unless parity was adjusted for. Unexpectedly, migrants from mainland China delivered heavier rather than lighter babies (each P<0.05). Type of living quarters and parental relation were also related to birth weight and low birth weight (each P<0.05). Continuous monitoring of the social patterns of birth weight is recommended.

Birth Weight↗

A study of demographic changes under sustained below-replacement fertility in Hong Kong SAR.

The total fertility in Hong Kong SAR fell continuously below replacement in the past two decades and reached a level of 0.98 in 1998. The rate in 1981 was close to replacement at 1.93. In this paper the theoretical outcomes of long-lasting below-replacement fertility are identified with a view to gaining some analytical insight into the situation, where the population is experiencing such a striking demographic trend. In the absence of migration, Hong Kong SAR will see its population start to decline between 2008 and 2038, if the future course of fertility falls within these 'bounds'. Concurrently, the aging of population will be reaching unprecedented proportions. Should fertility remain at the present below-replacement level, i.e. the worse-case scenario, the proportion of population aged 65 years or older would increase to 44 per cent, and those aged under 15 years would decrease to six per cent, by 2048. As a result, the potential labour supply (those aged 15-64 years) would dwindle to only 50 per cent of the population, suggesting that there would be less than one person potentially working to support one dependent (who is likely to be a person aged 65 years or older). The socio-economic consequences of population aging are discussed. By analysing net immigration in the demographic process in the past, the way in which replacement migration would help alleviate the problem of population decline and population aging is also discussed.

Adolescent↗

Association between size at birth, paediatric diarrhoeal incidence and postnatal growth.

UNLABELLED: This study tests the hypothesis that size at birth is associated with diarrhoeal incidence from birth to 24 mo of age, and the hypothesis that diarrhoeal incidence from birth to 24 mo is associated with body size at age 24 mo. This is a longitudinal study of 1476 infants born in Lahore. Pakistan, in 1984-1987. Diarrhoeal incidence was enumerated monthly. A generalized estimating equations approach with Poisson regression showed that birthlength standard deviation score (SDS) and ponderal index at birth (rate ratio = 1.01 and 1.00; each p > 0.05) were not significantly associated with diarrhoeal incidence. Multiple linear regression showed that diarrhoeal incidence was significantly associated with weight SDS and body mass index at 24 mo (regression coefficient or beta = -0.58 and -1.02: each p < 0.05). but not with height SDS (beta = -0.10: p > 0.05). The associations were mainly due to a transient effect of diarrhoea in the period 18-24 mo. CONCLUSION: Prevention of low birthweight is unlikely to have an impact on diarrhoeal incidence in infants. Control of diarrhoeal incidence may not improve the growth of infants in developing countries.

Birth Weight↗

Fetal growth, early postnatal growth and motor development in Pakistani infants.

BACKGROUND: Studies have often compared the postnatal motor development of 'small' versus 'normal' newborns. Not much is known about the associations between a broad spectrum of size at birth and motor development. The effect of early postnatal growth on motor development is little researched. Growth failure in terms of shortness and thinness should be differentiated, but not many studies have the data for this analysis. METHODS: This is a longitudinal study of infants born in Lahore, Pakistan, between 1984 and 1987. Age at commencement of independent walking and age at 'building a 3-cube tower' were taken as indicators of gross and fine motor development, respectively. Size at birth was captured by length and thinness as continuous variables; postnatal growth from birth to 6 months of age was measured by changes in length and thinness. Adjustment for covariates and handling of censored cases were performed by generalized log gamma regression. RESULTS: Thinness at birth and postnatal stunting and wasting had a linear, inverse association with gross motor development (each P < 0.05). Birth length had a non-linear, inverse association with this outcome (P < 0.05). Birth length, thinness at birth and postnatal wasting had a linear, inverse association with fine motor development (each P < 0.05). CONCLUSION: Both fetal and early postnatal growth over a broad spectrum may affect infants' motor development. It is not just the babies who were very small at birth that suffered. Birth length appeared to be more influential than other anthropometric indicators.

Child Development↗

An epidemiological profile of suicides in Beijing, China.

Suicide rates in the Beijing region increase with age. The rural suicide rate is about two to five times of the urban in various age-sex groups. The elderly suicide rate is very serious, especially in the rural area. The average suicide rate for the Beijing region for the period 1987-1996 was 9.8 per 100,000 (6.0 and 17.3 for urban and rural areas, respectively). A low male-to-female ratio was also observed. The female suicide rate for the 15-34 age group was higher than that of its male counterparts, which is unique in other areas of the world. These phenomena can be explained by some of the distinct cultural and economic traits of China. Also, suicides rates in the Beijing region were shown to be on a decreasing trend among the teenaged and the old-age groups. Our findings suggest that the suicide rate in China should not be as high as the estimated rate (31.0 per 100,000), suggested in the Global Health Statistics by Murray and Lopez (1996b, p. 824).

Adolescent↗

Suicide in response to changing societies.

The "medical model" is an insufficient explanation for the high suicide rates, but it does not mean that suicide is a different phenomenon in China. A multidimensional model (Fig. 6) is proposed to appreciate better the complexity of the problem, which can be applied to other countries. As in Figure 6, suicide and suicide attempts are conceptualized as a continuum of behaviors. The suicide method may modify the boundaries (i.e., the availability and choice of a lethal method may expand the size of completed suicides and vice versa). The spectrum of behaviors is also under the influence of individual factors, such as psychiatric disorders and personality, and local factors, such as local cultural norms, resources, and familial problems. All of these factors are subject to the influence of greater social forces. For example, psychiatric disorder increases the risk of suicide but is shaped by global forces. In the case of China, the importing of Western values influences the way Chinese people present their idioms of distress. Chinese people who tend to somatize start to psychologize more, [figure: see text] which in turn affects the rates of depression and subsequently the risk of suicide. The various factors also interact with one another. The diagnosis of disruptive and antisocial disorder illustrates how local factors modulate that of the individual. In Diagnostic and Statistical Manual of Mental Disorders, conduct disorder is defined by a series of "socially unacceptable behaviors," including aggression, destruction of property, theft, and violation of rules. Because biologic validity is lacking, the diagnosis (an individual factor) may vary widely in different cultural settings (a local factor). In China, conformity, self-control, and discipline are emphasized; subthreshold cases in the West already may be unacceptable in the Chinese setting and be labeled "disruptive." On the other hand, the cultural emphasis on conformity in the upbringing may reduce the display of such behaviors and lead to a lower prevalence of disruptive and antisocial disorders in China. With globalization, however, the "Chinese" values are more closely identified with the global culture, and a rising trend of personality disorders has been witnessed. The media are some of the powerful agents in transmitting these forces. The medical model of explaining the phenomenon of suicide with psychiatric disorders is not entirely satisfactory. The association of a high suicide rate with a low prevalence of psychiatric disorders in China challenges this conventional view. Rather than refuting this conventional model, the dynamic interaction with local sociocultural factors and global forces is emphasized. Empirical evidence is lacking, however, and should be the focus for future suicide research.

Adolescent↗

Further evaluation on long-term depot-medroxyprogesterone acetate use and bone mineral density: a longitudinal cohort study.

Cross-sectional studies on the effects of depot-medroxyprogesterone acetate (DMPA) on bone mineral density (BMD) have been controversial. The present longitudinal cohort study on 59 Chinese women over a period of 3 years has shown that their annual rate of bone loss at 3 sites (0.44% in lumbar spine, 0.40% in neck of femur, 1.05% in Ward's triangle) was substantially less than the projected values (1.1% in lumbar spine, 2.3% in neck of femur, 3.5% in Ward's triangle) in a cross-sectional study that had demonstrated a significant reduction in BMD in DMPA users than the non-user population. The trochanter BMD measurement did not show the projected annual bone loss of 2.4%. The rate of bone loss is probably non-linear, with a rapid loss in the first 5 years and a leveling off afterwards. The duration of DMPA use was not significantly correlated with the rate of bone loss. Multiple linear regression analysis demonstrated that age and body mass index were significant variables in modeling the rate of bone loss in the lumbar spine and neck of femur, but not in the trochanter and Ward's triangle areas. The Z scores also suggested a retardation in bone loss with time and potentially due to the effect of progesterone in decreasing bone turnover that is similar to the situation in postmenopausal women. The present data provide another aspect of reassurance to the long-term use of DMPA.

Adult↗

Seasonal variation in suicides: diminished or vanished. Experience from England and Wales, 1982-1996.

BACKGROUND: Seasonal variation in suicidal death has been observed in many countries. In particular, a cyclic variation was found for both men and women in England and Wales in the 1960s and 1970s. Men showed a single 12-month cycle whereas women showed two cycles. AIMS: To re-examine the seasonal variation in suicides in England and Wales for the period 1982-1996. METHOD: A harmonic analysis was used to detect the seasonality of the suicide data. RESULTS: The seasonal effect on suicide is greatly diminished in England and Wales. This is shown by the reduced amplitude and smaller proportion of variance accounted for by the season. CONCLUSIONS: The seasonal effect on suicide has either diminished or vanished.

Adolescent↗

Acute renal failure after immersion in seawater polluted by diesel oil.

Acute renal failure after exposure to toxic doses of hydrocarbon has been uniformly associated with multiorgan failure. We report a case of isolated acute renal failure in a patient after immersion in seawater polluted by diesel oil. The sites of absorption were likely to be skin, gastrointestinal tract, and lung. Investigations showed renal impairment as the only consequence from the exposure. The patient recovered uneventfully and did not require dialysis. This case highlighted the unusual consequence of isolated renal involvement resulting from hydrocarbon toxicity.

Acute Kidney Injury↗

Abnormal expression or mutation of TP53 and HPV in vulvar cancer.

HPV (human papillomavirus) plays an important role in cervical cancer and may also play a role in vulvar cancer. TP53 mutation is common in a variety of cancers but its role in vulvar cancer is not well established. The aim of this study was to assess the prevalence of HPV infection and TP53 mutation as well as their correlation in vulvar cancer. Also, HPV detection and abnormal p53 expression were assessed in relation to age, co-existing vulvar intraepithelial neoplasia and vulvar dystrophy. Forty-eight samples of vulvar cancer were studied. DNA was extracted from formalin-fixed paraffin embedded tissue for polymerase chain reaction/Southern blot study with HPV 16 and 18 and L1 primers. Paraffin sections were immunostained (IHS) for p53 protein using three antibodies, p1801, CM1 and DO7. The p53 mutation was also screened using polymerase chain reaction (PCR) single-stranded conformation polymorphism (SSCP) and confirmed by sequencing. Overall, HPV was detected in 48% (23/48), of which 96% (22/23) were HPV 16 or 18. By IHS, p53 overexpression was detected in 46% of cases whilst TP53 mutations were identified in 21%. In HPV positive and negative tumours, p53 abnormal expression was detected in 39% and 52%, respectively, and TP53 mutation was found in 22% and 20%, respectively. Mutations were mainly found at codons 273 and 204. Age was not found to be associated with HPV detection. However, the presence of HPV (71%) or absence of abnormal p53 expression (65%) were higher in tumours with VIN3, but were not correlated with dystrophy.

Aged↗

Estimation of the size of an open population from capture-recapture data using weighted martingale methods.

A weighted martingale method, akin to a moving average, is proposed to allow the use of modified closed-population methods in the estimation of the size of a smoothly changing open population when there are frequent capture occasions. We concentrate here on modifications to martingale estimating functions for model Mt, but a wide range of closed-population estimators may be modified in this fashion. The method is motivated by and applied to weekly capture-recapture data from the Mai Po bird sanctuary in Hong Kong. Simulations show that the weighted martingale estimator compared well with the Jolly-Seber estimator when the conditions for the latter to be valid are met, and it performed far better when individuals were allowed to leave and reenter the population. Expressions are derived for the asymptotic bias and variance of the estimator in an appendix.

Animals↗

Estimation of population size based on additive hazards models for continuous-time recapture experiments.

We use the semiparametric additive hazards model to formulate the effects of individual covariates on the capture rates in the continuous-time capture-recapture experiment, and then construct a Horvitz-Thompson-type estimator for the unknown population size. The resulting estimator is consistent and asymptotically normal with an easily estimated variance. Simulation studies show that the asymptotic approximations are adequate for practical use when the average capture probabilities exceed .5. Ignoring covariates would underestimate the population size and the coverage probability is poor. A wildlife example is provided.

Animals↗